1. Field of the Invention
This invention relates to a process for producing a solid catalyst component for olefin polymerization. More particularly it relates to a process for producing a spherical solid catalyst component for olefin polymerization, having a large particle diameter.
2. Description of the Related Art
As catalysts for olefin polymerization, Ziegler Natta catalysts have generally been used. As one of the catalysts, a supported type catalyst using a magnesium compound as a carrier is known, and a number of patent literatures directed to those exhibiting a superior polymerization activity have been reported. It is preferred for such a supported type catalyst to control the shape of the catalyst particles, and some processes therefor have been known, but they are insufficient as a process for obtaining a solid catalyst component having a large particle diameter and a spherical shape.
As one of such processes, there is disclosed a melt-quenching process of emulsifying the melt of the carrier component in a suitable oil to form spherical molten particles, followed by adding the particles into a cooled hydrocarbon medium to rapidly solidifying them (Japanese patent application laid-open Nos. Sho 55-135,102, Sho 55-135,103 and Sho 56-67,311). However, such a process raised problems that when the carrier particles are prepared, it is necessary to use a surfactant or the like, or voids are present inside the particles or sufficiently large particles cannot be obtained, etc.
Further, as a separate process, spray-drying process and spray-cooling process are known. According to spray-drying process (Japanese patent application laid-open Nos. Sho 49-65,999, Sho 52-38,590, Sho 58-45,206, Sho 57-198,709, Sho 59-131,606 and Sho 63-289,005), a solution of a magnesium compound in water or an alcohol is sprayed into heated nitrogen gas current to allow water or the alcohol to vaporize from the resulting droplets by the heated nitrogen gas and thereby obtain spherical solid carrier particles. However, this process raised a problem that since the solvent continuously and rapidly vaporizes from the particles, the resulting particles are porous, indefinite in the solvent content and unhomogeneous.
Further, according to the spray-cooling process (Japanese patent application laid-open No. Sho 63-503,550), a magnesium compound of the formula MgCl.sub.2.xLOH.ySKY in molten state is sprayed into a chamber cooled by a cooling inert fluid to obtain spherical solid carrier particles without vaporization of solvent. However, the process has drawbacks that the shape of the carrier particles obtained according to this process is often insufficient and the particles are broken when subjected to treatment with titanium halides.